No, they can't. Even if it may seem unfair to compare one against another, they are actually each judged on their own merit against the judging criteria.
It has been brought up before, and besides the fact they are not judged against another piece, the judges enjoy having the variety.
If the Challenge were separated between poetry and fiction, we'd also have to have a division for non-fiction personal reflection pieces, devotionals, and the list could go on and on.
There are no favorite styles or genres when it comes to judging the Challenge. The thing that jumps out is a fresh, creative approach that has been crafted well. Whether it's poetry or prose really doesn't figure in the equation at all.